noisy cable?

Harald Welte laforge at
Tue Mar 30 01:41:45 UTC 2010

On Mon, Mar 29, 2010 at 12:39:35PM +0200, willem wrote:
> i managed to get hello_world working on my c121, connected through a
> pl2303 usb/serial cable to my macbookpro.
> but found that the connection is extremely noisy.
> often the movement of me putting down the phone on the table is enough
> to break the upload.
> is that a common problem with these headphone/serial cable plugs?

no. maybe something about your cable or plug or socket in the phone?  I
only get unreliable/noisy transmissions if the plug is not properly
inserted all the way to the end (which is likely since the plug housing
diameter is typically a bit larger than what the phone case can take
unless you remove the PCB from the phone, or have a very low-diameter
plug housing of your cable.

Initially I was using a 2.5mm to 3.5mm headphone adapter cable (the ones
for attaching regular 3.5mm headphones to phones that have a 2.5mm plug,
as those plugs are smaller than anything I've seen from the T191 serial
cables so far).

> +    /* ignore modem status lines */
> +    options.c_cflag |= CLOCAL;
> +

This is something I pondered of doing anyway... it simply made no
difference on Linux / pl2303 so I never bothered...

But I'm happy to merge it.

- Harald Welte <laforge at> 
"Privacy in residential applications is a desirable marketing option."
                                                  (ETSI EN 300 175-7 Ch. A6)

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